1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of removing metals, such as nickel, titanium or cobalt in the fabrication of integrated circuits. The invention further relates to the recovery of the metals.
2) Description of the Prior Art
In the fabrication of integrated circuits, metal silicides are often formed through a rapid thermal annealing (RTA) process. Metals such as titanium, cobalt, and nickel are typically used in silicidation. After RTA, the unreacted metal is typically removed by wet chemicals. For example, SC-1 (Standard Clean-1 comprising ammonium hydroxide, hydrogen peroxide, and de-ionized water) may be used to remove titanium, SC-2 (Standard Clean-2 comprising hydrochloric acid, hydrogen peroxide, and deionized water) and a mixture of sulfuric acid, hydrogen peroxide, and water (SPM) may be used to remove cobalt and nickel. Nitric acid and SPM are also used for the stripping (rework) of cobalt and nickel on bare silicon wafers. The drawbacks of using wet chemicals include the expensiveness of high purity chemicals, disposal costs, and the corrosive nature of the chemicals.
U.S. Pat No. 6,225,202B1 (Gupta et al) teaches a method for removing unreacted nickel or cobalt after silicidation wherein the unreacted nickel or cobalt layer is exposed to a plasma containing carbon monoxide gas. The carbon monoxide gas reacts with the unreacted nickel or cobalt thereby removing the unreacted nickel or cobalt from the substrate to complete salicidation of the integrated circuit device.
U.S. Pat. No. 4,778,536(Grebinski) teaches a method to strip resist in a short period of time wherein the object is positioned with the surface exposed to both a water vapor and sulfur trioxide vapor adjacent to the surface to provide a hot mixture comprising sulfur trioxide, water and sulfuric acid. Energy requirements are relatively low since the components are easily vaporized.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering U.S. Pat No. 6,231,775(Levenson et al.) shows a process for the ashing of an organic film which comprises a plasma.
U.S. Pat. No. 6,242,165B1(Vaartstra) shows an organic removal process.
U.S. Pat. No. 5,358,601(Cathey) shows an etch process for a multi-layered structure including suicides.
U.S. Pat. No. 4,778,536(Grebinski) teaches a method to strip resist wherein the surface is exposed to both a water vapor and sulfur trioxide vapor adjacent to the surface to provide a hot mixture comprising sulfur trioxide, water and sulfuric acid.
U.S. Pat. No. 3,985,597(Zielinski) reveals a passivated metal interconnect process.
U.S. Pat. No. 5,259,923(Hori et al.) shows a multi-layer etch including suicides.
An object of an embodiment of the invention is to provide a method of removing a metal using S and O containing gas.
An object of an embodiment of the present invention is to provide an effective and easily manufacturable method of removing unreacted metal after silicidation using a two step, dry then wet, treatment.
A further object of an embodiment of the invention is to provide a method of removing unwanted metal using wet-dry treatment comprising a gas or a mixture of gases followed by liquid treatment.
Yet another object of an embodiment is to provide a method of removing unreacted titanium, nickel or cobalt after silicidation using two step dry-wet treatment.
Yet another object of an embodiment is to provide a method of removing unwanted titanium, nickel or cobalt using dry-wet treatment wherein the dry portion of the dry-wet treatment comprises a gas or a mixture of gases.
Yet another object of an embodiment is to provide a method of removing unwanted titanium, nickel or cobalt using dry-wet treatment wherein the wet portion of the dry-wet treatment comprises a liquid.
Yet another object of an embodiment is to provide a method of removing unwanted nickel or cobalt using dry-wet treatment wherein the gas or a mixture of gases in the dry portion of the dry-wet treatment is selected from a group comprising sulfur trioxide and sulfur dioxide.
Yet another object of an embodiment is to provide a method of removing unwanted nickel or cobalt using dry-wet treatment wherein the wet portion of the dry-wet treatment comprises deionized water.
The present invention provides an embodiment to remove a metal from over a substrate in the fabrication of an integrated circuit device. The embodiment comprises providing a metal layer over a substrate; removing the metal layer by reacting the metal layer with a reactant gas to form at least a solid product; the reactant gas contains at least S and O; then dissolving the solid product in a liquid, thereby removing at least portion of the metal layer from over the substrate.
Another aspect of a preferred embodiment is a method for removing nickel, titanium or cobalt using dry-wet treatment in the manufacture of an integrated circuit. A metal, such as nickel, titanium or cobalt layer on a substrate is exposed to a gas or a mixture of gases selected from a group comprising sulfur trioxide and sulfur dioxide wherein the gas or the mixture of gases reacts with the metal to form a product. The product is then removed through dissolution in a liquid, thereby removing the metal from the substrate.
Also in accordance with the objects of the invention a method for removing unreacted nickel or cobalt after silicidation using dry-wet treatment is provided. Shallow trench isolation regions are formed in a semiconductor substrate surrounding and electrically isolating an active area from other active areas. A gate electrode and associated source and drain regions are formed in the active area wherein dielectric spacers are formed on sidewalls of the gate electrode. A nickel or cobalt layer is deposited over the gate electrode and associated source and drain regions. The semiconductor substrate is annealed whereby the nickel or cobalt layer overlying the gate electrode and said source and drain regions reacts to form a nickel or cobalt silicide layer and wherein the nickel or cobalt layer overlying the dielectric spacers and the shallow trench isolation regions is unreacted. The unreacted nickel or cobalt layer is exposed to a gas or a mixture of gases selected from a group comprising sulfur trioxide and sulfur dioxide wherein the gas or the mixture of gases reacts with the metal to form a product which is then removed through dissolution in a liquid, thereby removing the metal from the substrate to complete the silicidation of the integrated circuit device.
Additional objects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of instrumentalities and combinations particularly pointed out in the append claims.